The overall objective of our proposed research is to determine how the components of the photoreceptor membrane are synthesized and assembled into the disc membrane unit of the outer segment, and then to elucidate the molecular events involved in the function of this membrane. We would like to discover if disc membrane renewal is regulated by the availability of its component lipids and proteins, and to determine if a deficiency in one of these components has an effect on membrane function. As a preliminary to these objectives, we want to determine the pathways of phospholipid and fatty acid biosynthesis in the photoreceptor. We want to determine the extent to which the pigment epithelium is involved in, or affects, the synthesis of the disc membrane by the photoreceptor inner segment, as well as its role in regeneration of visual pigment. Additionally, we would like to discover the cellular site at which the chromophore is added to visual pigment, and then see if visual pigment is present in the plasma membrane of the cell. Hopefully, these experiments will have broad and general applications to membrane biology as well as important specific applications to photoreceptor function and vision as a whole. BIBLIOGRAPHIC REFERENCES: Basinger, S.F., Bok, D., and Hall, M. (1976). Rhodopsin in the rod outer segment plasma membrane. J. Cell Biol. in press. Basinger, S., Hoffman, R., and Matthes, M. (1976). Phosphatidyl choline metabolism in the frog rod photoreceptor. Exp. Eye Res. in press.